The invention relates to a burner for hard-to-ignite mixtures, such as exhaust gases of an internal combustion engine.
The term "hard-to-ignite mixtures," as used herein in connection with the invention, means mixtures that contain either little oxygen or fuels that are hard to burn, i.e., are relatively incombustible in comparison to typical fuels, such as fuel oils, kerosene and gasoline. A filtering device in the exhaust gas tract of a diesel internal combustion engine in which a so called exhaust gas burner is used, to combust a mixture wherein exhaust gases serve as the combustion air source (i.e., as the oxygen carrier), for producing heat that will cause regeneration of the filtering unit by burning off accumulated soot particles and the like, is an important example of a situation where a need to combust a hard-to-ignite mixture exists, and is described in commonly owned U.S. patent applications Ser. Nos. 196, 557 and 196,558 by one of the present co-inventors, filed on May 20, 1988.
In such exhaust gas filtering units of diesel engines, the quantity of oxygen in the exhaust gas is subject to great fluctuations and these fluctuations are especially dependent on the momentary operating point in the engine family of characteristics. However, if the oxygen content in the exhaust gas is small, igniting such a burner causes extremely great difficulties, even with good mixing of fuel and exhaust gas. With good, thorough mixing, the residual oxygen can support combustion. However, igniting of the mixture is practically impossible, or possible only with great ignition energy.